Project Summary Obesity continues to be a major health crisis, afflicting populations worldwide with comorbidities that include type 2 diabetes and cardiovascular disease. This has stimulated research of neural circuits regulating energy balance, and technological advances have allowed for the dissection of genetically-defined brain circuits controlling feeding behavior and physiology. Studies have revealed complex central circuits, which ultimately exist for integrating endocrine and peripheral sensory signals. The vagus nerve is a critical sensory pathway for the control of meal termination and is the only direct neural link between the gut and brain. Vagal sensory afferents innervate the gastrointestinal tract and inform the brain of the quantity and quality of food being consumed. Similar to other neural systems, the vagus nerve contains heterogeneous neuronal populations that have discrete connections and perform specialized functions. However, most of what is known about the vagus and behavior comes from non-specific surgical and chemical ablation studies that do not provide mechanistic insight about distinct neuronal populations. Hence, little is known regarding primary sensory signals directly related to satiation, and research in this area is imperative for understanding the central organization and regulation of energy homeostasis. Studies in this proposal will utilize state-of-the-art wireless technology and viral/transgenic techniques to manipulate genetically defined vagal afferent neurons innervating the stomach. We will examine the relative roles of distinct gastric vagal afferent neurons in the control of food intake, which could potentially lead to the identification of novel therapeutic targets for the safe and effective treatment of obesity. 1